Current electrical requirements for heavy-duty diesel engines, for example, require several electrical inputs to the Engine Control Unit (ECU) from the electronic throttle control. These inputs are typically a single analog signal, which changes in response to the driver's request for fuel, and a position switching function which is a signal to the engine that the throttle is at idle or is at some other specific point. These position sensors have typically been mechanical contact electrical devices.
Non-contact electronic sensors are emerging as the sensor of choice for a variety of reasons. Non-contact sensors, however, may not be able to provide the switch using the existing wiring and electrical strategies. One such switch type that non-contact sensors are incompatible with is a switch type known as a form “C” switch.
FIG. 1 illustrates an electrical diagram of a typical ECU for an Idle Validation Switch (IVS) input that may be implemented using a form “C” switch. Such inputs may be provided to the form “C” switching device to allow the ECU to sense the state of the Normally Open (NO) and Normally Closed (NC) signals associated with the IVS. Form C switches are implemented either such that one contact is broken before the second contact is made, which is typically referred to as “break before make” or both contacts are made at the same time, which is referred to as “make before break”.
Certain engine manufacturers may require that the source of ground and power to the IVS and the Accelerator Position Sensor (APS) be independent of one another. Such a requirement would limit the switching apparatus such that the apparatus may not use the same ground and power source that the APS uses. This typically does not present a problem for contact type resistive potentiometers, as they typically use the completion of a circuit to register the switching function. Because a non-contact sensor may use active electronic devices, however, each of the IVS and APS functions may have its own source of power and ground, independent of the other. A form C switch, for example, requires three wires to implement the common (COM), normally closed (NC) and normally open (NO) terms, where one wire is a common return and the other two wires carry the NC and NO signals to the engine control unit. A typical APS may also require three wires to implement the device.
Therefore the typical wiring harnesses for vehicles only requires a 6-wire interface which may be incompatible with non-contact sensors. Currently, to accommodate non-contact sensors, vehicle manufacturers must change their wiring harness and connector configuration to add a seventh wire in order to accommodate the additional power or ground reference.